We believe that altered intracellular fluxes of calcium are meaningful to a wide variety of clinical and experimental observations in cystic fibrosis (CF). We and others have demonstrated that cultured skin fibroblasts are a suitable model for studying CF. In this proposal we plan to pursue our discoveries of premature senescence and increased intracellular calcium (Ca) pools in fibroblasts from CF. We have also traced the site of the Ca difference to mitochondria. Our objectives are to confirm and/or extend observations concerning (1) premature senescence in CF cells (as assayed by plating efficiency, cell population doubling and incorporation of tritiated thymidine into DNA), (2) increased resistance to sterol drugs, (3) increased induction of alkaline phosphatase in CF cells and (4) increased O2 consumption by CF cells. We shall study how intracellular calcium modulates these effects and whether manipulation of intracellular calcium can reverse them. In order to accomplish these objectives we shall use the following techniques: cell culture, plating efficiency, cell population kinetics, radioactive tracers (45Ca and 3H-TdR), atomic absorption spectrometry, and O2 consumption.